How to make toon (cel) shader with 3 colors?

How to make toon (cel) shader with 3 colors in Unity 5? Help me pleas.

Create a custom lighting model

In the example you will see c.rgb = s.Albedo * _LightColor0.rgb * (NdotL * atten);

Your per-pixel light value will be NdotL * atten (dot product + shadows)

If you only want only 3 shades of light, you could change it to this: round(saturate(NdotL * atten)*3)/3
That will create this effect: alt text